The present invention relates to a product with a diffractive microstructure. The present invention also relates to a method for manufacturing a product having diffractive microstructure areas and a device for producing diffractive microstructure areas on the surface layer of a paper or cardboard substrate by embossing.
Diffractive microstructure areas may be attached to products e.g. for producing a visual effect or for authenticating the product.
Diffractive microstructures may be produced e.g. by embossing the surface of a substrate coated with a suitable lacquer. When producing the microstructure, the substrate is pressed between an embossing member and a backing member. The surface of the embossing member comprises a relief corresponding to the microstructure. During the embossing process, the backing member supports the substrate from the back side so that a sufficient pressure may be exerted on the surface of the substrate for shaping the surface layer of the substrate to correspond to the relief of the embossing member.
U.S. Pat. No. 4,913,858 discloses a method for producing a diffractive microstructure on the surface of a paper coated with a thermoplastic material. The microstructure is formed into the coating by using a heated embossing roll.